Means for cleaning wood-cutting dies



2 Sheets-Sheet 1 PER OLOF SKOOG INVENTOR.

BY 7 M, M

May 17, 1960 P. o. SKOOG MEANS FOR CLEANING WOOD-CUTTING mas Filed Feb. 11, 1957 y 1960 P. o. SKOOG MEANS FOR CLEANING WOOD-CUTTING DIES 2 Sheets-Sheet 2 Filed Feb. 11., 1957 Julm mum; OF

to 0523 Om g PER OLOF SKOOG INVENTOR.

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BY 7M United States Patent This present invention relates to the general art of diecutting wood patches of various shapes from veneer 2,936,802 Patented May 17, 1960 2 chines, so there will be no substantial buildup of pitch or resins which will interfere with the proper functioning of the cut and rejected portion of the veneer during the patching cycle.

A further object of this invention is to provide means for cleaning veneer-cutting dies, which consists of treating the inside of the dies'dun'ng each cycle of operation with a pitch or resin solvent in such quantities as to soften and dissolve the thin film that may be deposited in each cycle, but to use the solvent in such limited quantities that it will not interfere with the gluing operation of the plies.

A further object of this invention is to provide means for introducing and distributing a very small amount of pitch or resin solvent at the proper period of each cycle of operation of the plywood patching machine.

stock, such as used in patching of plywood sheets. More specifically, this invention relates to means for cleaning the resinous or pitch-like materials from the inside of the female die, to the end that patches of the desired type can be produced uniformly without the unsupported edges of the patches being broken off during the patchproducing cycle of the typical machines used in this field.

In the manufacture of plywood many machines are in use, which have the sole purpose of cutting a deto substantially simultaneously cut a patch to fit the opening thus provided and seat the new patch in the opening previously formed. Such patching has proved to be practical, in that itrestores the sheet to full usefulness and results in the upgrading of the whole plywood panel.

it is normally necessary to make the diameter, or in case of non-circular patches to have the size of the scrap ejector somewhat smaller than the actual cutting die size, in order to let the hole-cutting knife complete its operation before energizing the plunger for the ejection of the scrap. Therefore, there is not a complete supporting of the cut-out scrap when it is ejected through the die.

It is'normally desirable to have the grain of the patch run in the same direction as the grain of the veneer being patched; and, while the wood fibers in the medial portion of the patch can stand some overhang where they are not supported, the cross-grained fibers form- 'ing the wood particles on the two opposite edges of the patch or scrap similarly extend beyond the ejector plunger and are unsupported except for the limited support effect of the cross-grained material.

There is a tendency for these edges tobreak off under normal conditions, but, as long as the inside surfaces of the female die are smooth and clean, there is very little actual breakage of these margins even in the cross-grained areas. However, when pitch or other wood resins, in both the cut-out and'the new patch,'wipe onthe inside faces of the female die, a deposit forms there in a film, thick enough and tough enough to cause very considerable friction in the passage of a defect patch through the'die.

This results in numerous instances of the scrap edges pieces are often left on top of the finished patch, causing --a problemof removal. If they are left there, they may 'fective portion out of'a sheet of plywood veneer and Because'of the sequential operations involved be pressed into the sheet by' either the adjacent patching of this area in a sheet; or, when the sheets are pressed into plywood, these pieces of scrap become embedded in the surface of the plywood panel, causing the panel to be marred and to be downgraded, which is contrary to i 'the objects sought in the patching of plywood.

The principal object of this present invention, therefore, is to provide means for'cleaning the interior surfaces of the veneer-cutting dies, as used in plywood patching main US. Patents Nos. 2,336,703 and 2,336,704, and show-' ing further the inclusion of a portion of the means making it possible to achieve the principal objects of this invention.

Figure 2 is an enlarged portion showing the die structure more clearly than could be shown on the reduced scale of Figure 1.

Figure '3 is a diagrammatic view illustrating the flow of air and solvent through the equipment necessary to produce a cleaning or solvent vapor of the type required;

Figure 4 is a bracketed view showing some typical shapes of the patches normally used in patching plywood veneer.

Referring more particularly to the disclosure in the drawings, the numerals 10 and 12 designate, respectively, the male veneer-cutting die and the female or table die associated therewith. Many different forms of die structures are employed in this field, and the present illustrations are merely illustrative of one form of these dies. However, the problem noted in the preamble of this application is present in substantially all forms of dies which cut a patch-like form from veneer sheet stock and is present in'the two operations: (1) the actual cuttingout of the defect in the veneer stock; and (2) where a patch is cut, also from veneer stock, of a size to replace the cut-outportion.

Referring'to Figures 1 and 2 as being exemplary of this field of endeavor, die 12 is coaxially mounted with with die 12 to insure proper functioning the subsequent sequence of operations. Various means may be provided to lower and secure the holding member 16 in position. The next operation is to energize the cutting die or knife 10, and this is achieved by timing means including the cam arrangement shown at 18 in Figure l, the pivoted cam follower 19, driving through suitable linkage a cross- 'head member 20 which in turn transmits the cam-initiated energy to the downward movement of the knife 10.

Knife 10 progresses substantially to the point shown in Figure 2, at which time it has entered die 12 and completely severed the veneer patch or defect portion and produced the loose veneer piece indicated at 22. The

next operationin order is the ejection of wood particle 3 22 which must be forced downwardly through die 12 so as to clear the same. One convenient arrangement is shown in Figures 1 and 2, in which the ejector member 24 is forced downwardly, carrying with it portion 22, and Snag; discharging it from the bottom of the opening in During the cutting operation, while knife 10 is passing through the veneer stock, the ejector member must be retracted upwardly within knife, 10 and it must be raised substantially to the dotted line position 26 so that the knife portion will have free movement through the veneer and complete its out. It follows from this interference of parts that the ejector must necessarily be smaller than the interior of the knife, which in turn must pass or be capable of passing through die 12.. This creates the clearance shown at 30. The clearance at 39 produces a condition in which the veneer member 22 is not fully supported but must actually extend outwardly beyond the limits of ejector 24, and thus is created the condition wherein the cross-grained marginal portions of the cut veneer member tend to be rolled off the member, and this occurs normally as soon as die 12 becomes coated with any of the mucilaginous excretions from the wood, chief among these being pitches and resins of various types. Machines of this order, to be commercially feasible, must operate at a reasonably high cyclic rate, and consequently, even though a very minute amount of gummy material is left in the die through each cycle of use, it can soon accumulate to the point where it begins to interfere with the clean cutting functioning of the machine.

A practical solution of this problem, which can be adapted to the various types of patching machines that have been observed, is substantially as follows: To inject air which has suspended in it a mist or fog of solvent and which will prevent the buildup of resinous or pitchy materials in the table die 12 and maintain the inner surface 14 in a condition which permits the easy passing of the cut-out veneer items.

The type and quantity of solvent may need to be varied to meet the need for a solvent that will remove the particular type of pitch or resin carried by the wood. For most Woods of the type of fir and the like, kerosene or stove oil works quite satisfactorily. It is desirable, however, that the solvent used be a true solvent and not a lubricant, as the success of this whole operation rests in actually dissolving the small amount of the pitches, gums or resins left by the passage of the cut face of the wood material so the next following patch will wipe out and carry the resins, gums etc. away.

The desired solvent can best be introduced as a fog or mist and kerosene and like solvents can, by suitable carburetion devices, be introduced into air in atomized 'form and will be suspended by the air as long as it is in movement. Experience has proven that, by having the solvent carried in air, a small amount of solvent can be fully distributed over a relatively large'area, and that characteristic is a prime requisite for the successful operation of this method. By coating the die surfaces, and especially if done during each patching cycle, the mucilaginous excretions from the wood are prevented from affixing themselves to the metal of the die. It is very essential that the solvent be used in such a small quantity during each cycle of operation so that it will not occur in sufiicient amount on any of the cut surfaces to interfere with the satisfactory setting of the glues used in the plywood industry. I

In the following described exemplary form, the following preferred method is employed: Compressed air from some suitable source is suppliedto pipeline 40 and passes through the filter 42, so that it is delivered free of the impurities that might affect its ability to pickup the solvent or to leave unwanted liquids or materials on the plywood, which might interfere with the gluing operation. The filtered air, which is normally supplied ata pressure of 0 po or u d s. p ssed throu h. the pressur regulator 44 which should be set to deliver air to the air storage tank 46 at a pressure of from 20 to 40 pounds per square inch. It is then led through the top fitting of a fog type lubricator. These lubricators are common items on the market and consist normally of a bowl which is periodically filled with a liquid which it is desired to vaporize. It normally is provided with a siphon tube going to the bottom of the liquid-containing bowl, and at its upper end the siphon tube has a jet which is. in the line of draft created by the moving air, and thus a small amount of the solvent is picked up and atomized. into. a fog or mist which is then carried on through the mechanically operated valve 5t Valvefiti is illustrated in Figure 1 and consists of a body portion 52 employing a spring-seated ball 54-. This ball is periodically raised from its seat by the mechanically operated and spring-retracted piston rod 56. The agency driving this valve mechanism can be any part of the machine that completes its cycle of operation concurrently with the operational cycle of the die assembly 1t) and 12. in the type of mechanism shown in Figure 1, the cam follower 19' is an ideal actuating means as the timing for the movement of plunger 56 can be very accurately achieved by moving the valve 50 along follower 1.9. Valve 50 should be opened to permit the flow of the solvent-carrying air so that it may reach the interior chamber of die 12, preferably as the patch 22 being discharged has reached the bottom of die 12 and is being released.

The solvent-carrying air passes through piping. 57 and hose 58 where it is joined to an axially positioned tube 6! in the hollow tube which actuates-the patch ejector 24. The volume of pipe 57 and hose 58 between valve 50 and discharge openingstl causes a very appreciable drop in pressure due to the intermittent supply of fluid by valve50.

Tube 60 discharges the air and solvent out through radially disposed diametrically opposite openings as 62, so that the discharge is normally against the diametrically opposite sides of bore 14 and should be so placed that this impingement is in the area where the cross-grained margins of the patch normally rub on the wall 14. Tube 60 need not be in contact with the walls of the axial opening of member 24, as it is desirable that a minimum pressure remain in the air when it is discharged into the die chamber. Consequently any reasonable amount of clearance, which causes venting to the atmosphere, will not interfere with the successful operation of my device. An optimum pressure when the solvent-carrying air impinges upon wall 14 is in the range of 5 to 25 ounces per square inch pressure. Considerable air Will be released at this time in the interior of die 12, but, notwithstanding, it will probably be carrying, for the single puff of air discharged at each cycle, only a fraction of a drop of solvent. It has been found that, if the introduction of the solvent-carrying air can be likened to just a puff as one might exhale in breathing, the best results would be achieved in obtaining the most uniform coating of the side wall portions that are most critical, namely, the ones that are contacted by the cross-grained unsupported edges of the cut-out piece of plywood. Because of the manner of introducing a solvent in this form, it is possible to readily and accurately control the amount of solvent being deposited, and this is critical because, on one hand,

it is necessary to have enough solvent introduced to prevent resinous buildup and yet not enough excess solvent so that the patched veneer will be coated to a degree that might interfere with the gluing steps .of the plywood production. The exact amount to be used will depend, of course, on the type and size of dies; the frequency of the operational cycle; the type of pitch or resinous materials that must be dissolved; and, in certain instances, the yp of l used, as, ome ass a e l s a f by a solvent like kerosene and others.

It is very desirable that the solvent be deposited principally at the critical areas of wall 14 of the die 12, to

the end that a minimum amount'will be used. Experience has shown that high pressure deliveiy normally creates turbulence and distributes the solvent quite generally 3 over all of surface 14 which, as noted, is not desirable.

delivery pressures and must also be considered in the timing of the solvent application.

It is believed that it will be clearly apparent from the above description and the disclosure in the drawings that the invention comprehends a novel method and means for cleaning wood-cutting dies.

Having thus disclosed the invention, I claim:

Apparatus for punch-cutting wood veneer, comprising: a table having a female die opening therein including an upper shearing edge at the juncture of the wall of said opening with the top of said table and knife means therebelow forming a lower plug shear; and upper hollow male die element reciprocally cooperable with said upper shearing edge to cut a portion from veneer disposed over said female die opening; an ejector plunger in said hollow male die reciprocable from a position within said die eleasaaeaa meat to a position ther'ebelow and through said die opening of the female die to below said knife means, said hollow male die element including a void forming a fog chamber around said ejector plunger; means to reciprocate said hollow male die; means to reciprocate said ejector plunger; an air pressure source connectedby a conduit tosaid chamber; a solvent source in said conduit adapted to supply increments of solvent to air under pressure as it passes to said chamber; a valve in said conduit; and a timer operatively connected to said valve and phaserelated to said ejector plunger to open the valve coincidental with the entrance of said ejector plunger into said female die opening and to close the valve prior to the emergence of the ejector plunger from said lower plug shear whereby air-solvent fog is applied to the wall of said die opening.

References Cited in the file of this patent UNITED STATES PATENTS 231,679 Paxon Aug. 31, 1880 1,246,886 Cottrell et al. Nov. 20, 1917 1,319,108 Palmer Oct. 21, 1919 1,678,932 Buhler July 31, 1928 2,153,219 Walter Apr. 4, 1939 2,336,704 Skoog Dec. 14, 1943 2,488,835 Skoog Nov. 22, 1949 2,722,245 Clampitt Nov. 1, 1955 2,746,495 Greenlaw May 22, 19,56 

